|Year||July 23 1940
Sep 18 1940
|Weights and loads|
|Wing Load (kg/m2)|
|Power load (kg/hp)|
|Turn time||22sec at 1000m|
|Gun Type (Position)||Ammo|
|7.62mm ShKAS (engine)||2*500|
A.S.Yakovlev already was an author of successful trainers UT-2 and UT-1. Powered with 100hp M-11 engines, those airplanes were not suitable for pilots preparing to fly coming new generation fighters (I-26, I-200, I-301). Trainer conversions of N.N.Polikarpov (UTI-2 and UTI-4) were obsolete and were even more demanding than the 'parent' I-16.
But in 1940 A.S.Yakovlev already had light-weight fighter with excellent handling - I-26. It was clear that adding a second cockpit will not deteriorate its performance. More powerful derivatives of M-105 were under development.
On January 25, 1940, project was initiated by A.S.Yakovlev. It happened 12 days after first flight of the original single-seater. Formally approved by Governmental Order (March 4), aircraft was assembled June 17. Two prototypes were built, under designations UTI-26-1 and UTI-26-2. In technical documentation other designations may be found: UTI-26-4 and UTI-26-5 (following three I-26 prototypes), UTI-27-1 and UTI-27-2.
Both cockpits were covered with single plexiglas canopy, but pilot and instructor had separate sliding sections. Equipment of pilot's cockpit was practically identical to one of combat aircraft. Communications between pilot and instructor were performed by simple 'rubber communication device' - hose. Same device was used on early series trainers (Yak-7UTI) but soon was replaced by SPU-3 intercom. Navigation and electric equipment allowed only daytime flight, using land features for navigation. But removable screen allowed blind flight practicing.
Aircraft had dual flight controls, both instructor and pilot could operate landing gear brakes and retraction. 'Photogun' was installed in pilot's cockpit.
Armament was reduced to pair of machineguns. To compensate center of gravity shift, wing was moved 100mm backwards. Some improvements based on I-26 trials were introduced, but new trainer still shared most of the parts with combat aircraft.
Factory trials were performed by test-pilot/engineer P.Ya.Fedrovi and mechanic M.M.Schipanov between July 23 and August 25, 1940. Handling was almost identical to the I-26 and other modern fighters with liquid cooling engines. But number of serious defects were revealed:
Last defect was the worst, because engine start, landing gear operation, flap control, wheel brakes and guns reloading was performed from common pneumatic system.
Despite all those problems, UTI-26-1 was presented on State Trials (August 28 to September 25 1940). Flights were interrupted for 12 days when landing gear collapsed (again!) on taxi, damaging wing tip and propeller. Another interrupt took place on September 19, when UTI-26-1 was transferred to 11thIAP (Kubinka). For two days it was used to prepare pilots, who had to participate in service trials of the first series I-26 (built by factory N°301).
Team of NII VVS included senior pilots P.A.Stefanovskij and A.G.Kubyshkin, leading engineer N.I.Maksimov (since August 30 - A.T.Stepanets), engineers A.I.Khovanskij (engine and propeller), A.G.Aronov (weapons), V.K.Salikhov (special equipment), technician B.F.Sbitnev. Thirty flights (22h20min) were performed by nine pilots from 11thIAP under command of General-Major I.A.Lakeev (Hero of the Soviet Union).
Main conclusion was that UTI-26-1 (as well as I-26) was presented for State Trials too early, has large number of (curable) defects and needs serious refinement. But at the same time such trainer is desperately needed. It was recommended to present the second prototype (UTI-26-2) on state trials as soon as possible with all major defects of UTI-26-1 overcome.
Finally on September 25 UTI-26-1 was recommended for series production as the only trainer aircraft suitable for pilots transition to new generation of combat aircraft. It became the only advanced trainer of the VVS during the Great Patriotic War...
After trials UTI-26-1 was returned to OKB. Extensive program of upgrades was undertaken: new oil cooler, new engine, new air scoop, new system of landing gear locks were installed. 119 flights were performed (before December 10) to evaluate reliability of new systems. At the same time UTI-26-1 started its service of advanced trainer: 37 flights at Kubinka were performed to prepare pilots for first MiG-3 regiment.
The second prototype construction started on January 25 1940. During construction period design was revised many times to fix problems revealed during flights of UTI-26-1 and I-26 prototypes. As a result, UTI-26-2 was ready only on September 17, 1940. It differed from UTI-26-1 by increased area of tail control surfaces, large wheels and all-new reliable landing gear construction, new oil cooler, forward moved gravity center and number of smaller modifications.
Factory trials (September 16 to December 12) and special State Test Program (January 1 to February 14 1941) proved that I-26-2 is a success. Pilots and engineers of NII VVS performed 21 flights (12h55min). 260 aerobatic figures were performed. Trial results:
UTI-26 prototypes put the beginning to 'heavy' branch of A.S.Yakovlev WW-II fighters.
|Drawing by Igor Soultanov, used as a background for this page; ("History of aircraft construction in the USSR", Vol.2 p.196)|